1. Field of the Invention
The invention relates to an apparatus for high performance switching in local area communications networks such as token ring, ATM, Ethernet, Fast Ethernet, 1 gigabit and 10,000 Mbits/s Ethernet environments, generally known as LANs. In particular, the invention relates to a method and apparatus for enabling L3 switching in a stacking environment.
2. Description of the Related Art
As computer performance has increased in recent years, the demands on computer networks has significantly increased; faster computer processors and higher memory capabilities need networks with high bandwidth capabilities to enable high speed transfer of significant amounts of data. The well-known Ethernet technology, which is based upon numerous IEEE Ethernet standards, is one example of computer networking technology which has been able to be modified and improved to remain a viable computing technology. A more complete discussion of prior art networking systems can be found, for example, in SWITCHED AND FAST ETHERNET, by Breyer and Riley (Ziff-Davis, 1996), and numerous IEEE publications relating to IEEE 802 standards.
Based upon the Open Systems Interconnect (OSI) 7-layer reference model, network capabilities have grown through the development of repeaters, bridges, routers, and, more recently, “switches”, which operate with various types of communication media. Thickwire, thinwire, twisted pair, and optical fiber are examples of media which has been used for computer networks. Switches, as they relate to computer networking and to Ethernet, are hardware-based devices which control the flow of data packets or cells based upon destination address information which is available in each packet. A properly designed and implemented switch should be capable of receiving a packet and switching the packet to an appropriate output port at what is referred to wirespeed or linespeed, which is the maximum speed capability of the particular network.
Basic Ethernet wirespeed is up to 10 megabits per second, and Fast Ethernet is up to 100 megabits per second. The newest Ethernet is referred to as 10,000 Mbits/s Ethernet, and is capable of transmitting data over a network at a rate of up to 10,000 megabits per second. As speed has increased, design constraints and design requirements have become more and more complex with respect to following appropriate design and protocol rules and providing a low cost, commercially viable solution. For example, when switches are stacked, i.e. interconnected by a single link between “adjacent” switches, switching of incoming data based on the L3 level of the OSI model is made more complicated in that the correct destination module (switch) must be determined for the switching to be properly affected.
However, prior art switches and systems have limitations that can impede the overall effectiveness of such switching and can adversely affect the operational speed of a switch. Thus, there is a need to provide L3 switching of switched data through a network switch that does not impede the processing of data by that switch.